Pbx group hunting for communication switching systems



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oRlGaNATING OOOIO Aug. 29, 1967 ERASE `Il OOOO S30 OO |00 so |||oo sloucoo su noso sua o|o|o T0 TBR Aug. 29, 1967 F. B. slKoRsKl v PBX GROUPHUNTING FOR COMMUNICATION SWITCHING SYSTEMS 13 Sheets-Sheet l5 OriginalFiled Aug. 27, 1963 m X A B ND P Mn RI Ew MIE mv.R MM TS NE om mm OA HMO TA CLASS OF SERVICE /CSI United States Patent O 3,339,029 PBX GROUPHUNTING FOR COMMUNICATION SWHTCHING SYSTEMS Frank B. Sikorski, DesPlaines, Ill., assignor to Automatic Electric Laboratories, Inc.,Northlake, Ill., a corporation of Delaware Original application Aug. 27,1963, Ser. No. 304,826. Divided and this application Dec. 1, 1966, Ser.No.

6 Claims. (Cl. 179-18) ABSTRACT OF THE DISCLOSURE This is a division ofmy application Serial No. 304,826 filed Aug. 27, 1963, now abandoned,with claims identical to the allowed claims of the parent application,the only reason for filing this continuing application in place of theparent being to eliminate unnecessary details from the drawings anddescription. The drawings and the specification following the briefdescription of the drawings in the original application is identical tothat of an application by W. R. Wedmore for a Marker for a CommunicationSwitching Network, Ser. No. 804,892, filed Aug. 27, 1963, now Patent No.3,293,368 which may be referred to for additional details of the system.

This invention relates to a communication switching marker selectionarrangement, and more particularly to a PBX-group hunting arrangementfor a crosspoint switching network.

U.S. Patent No. 3,170,041 by K. K. Sp-ellnes issued Feb. 16, 1965,describes a Communication Switching System having marker controlledcrosspoint switching networks, and common control equipment comprisingregistersenders and translators. Each register-sender group includeselectronic apparatus sheared on a time division multiplex basis, with aferrite core array used in a recirculating arrangement. The systemprovides full translation on every call from the directory number to anequipment location number. 'Each subscriber in the exchange isidentified to the other subscribers by the office code, or one of anumber of ofiice codes, of that exchange and by a line directory number.His line is also assigned in that exchange a particular appearance on aset of terminals of the switching equipment. This arrangement permitscomplete flexibility in the assignment of telephone numbers andterminals on the switching equipment, and eliminates the necessity for aline intermediate distributing frame. Any change of subscriber serviceis accomplished simply by changing the instructions stored in thetranslator. T-he translator preferably uses a magnetic drum. Changes onthe drum are made simply by keying instructions in a control console.The translator equipment is arranged to be accessed from theregistersender groups. The translator assigns itself to a register atVarious times during dialing, for example at the end of a group ofdigits representing an ofiice code or other special code.

The switching network comprises local subscriber line groups of 1000lines each, selector groups, and incoming trunk groups. Each line groupprovides crosspoint switching matrices for originating connections fromcalling local subscriber lines to originating junctors which areconnected to selector inlets, and also through a register matrix toregister junctors; and also provides matrices for terminatingconnections between terminating junctors and called local subscriberlines, the terminating junctors being accessed directly from selectoroutlets.

The line group markers each include a line identifier to scan the linecircuits during an originating call cycle to select a line requestingservice, a register selector to select an idle register, a path selectorto find an available path through the network, and an arrangement toapply potentials to the network to establish a connection. A terminatingselector scans during a terminating cycle to select a terminatingjunetor to which a call has been extended from the selector. The markersalso each include a signaling circuit to receive called line numbersfrom the sender. The called number may designate a PBX group.

According to one feature of the invention, the same line identifier isused during a terminating call to a PBX group as is used to scan thelines during an originating call. The marker when in a terminating callcycle upon receiving switching control signals designating the PBX groupcauses a marking potential to be applied to the pull conductors at theline terminals for each line of the PBX group. For lines of the groupwhich are busy the cutoff relay is operated and shunts this potential toan opposite polarity point such as ground. For each idle line of the PBXgroup the potential appears to 'be a call request signal to the lineidentifier. A-t the same time the source of .potential which is commonto all of the line .relays is disconnected so that lines which haveactual calling service requests do not have calling potential applied totheir pull conductors. The line identifier now operates in the samemanner as during an originating call, and scans to set itsidentification devices for the marking potential received from one ofthe PBX lines, and thereby selects and records the identity of one ofthe idle PBX lines. Preferably the line identifier is set to a fixedinitial state before starting scanning so that Ithere is a fixed orderof preference for the lines of the PBX group.

A switching network is covered by Patent No. 3,275,752 for aCommunication Switching System, by M. H. Esperseth et al.; Patent No.3,211,837 by L. Bruglemans covers a Line Identifier Arrangement for aCommunications Switching System. The line identifier of the Bruglemanspatent makes use of the switching network described in the et al. patentfor identifying the calling line on originating calls. In a preferredembodiment of the invention this line identifier arrangement is alsoused for terminating calls to a PBX group to scan the lines and selectan idle line in the marked group.

The above-mentioned and other objects and features of this invention andthe manner of attaining them will become more apparent, and theinvention itself will be best understood, by reference to the lfollowingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings comprising FIGS. 1 to 15 wherein:

FIG. 1 comprises a block diagram of one line group for a telephoneswitching exchange showing a trunking diagram of the switching network,and a diagram of a marker;

FIG. 2 is a block diagram of the exchange;

FIGS. 3-6 comprise a schematic and block diagram of a line group andline group marker;

FIG. 7 is a diagram of a register-sender group, translator, and groupselector;

FIGS. 8-11 comprise a symbolic -block diagram of the marker send-receivecircuit;

FIG. 12 is a sequence liow chart;

FIG. 13 shows how FIGS. 3-7 are to be arranged;

FIG. 14 shows how FIGS. 8-11 are to be arranged; and

FIG. 15 is a schematic dra-wing of the class-of-service and PBX markingunits.

SYSTEM i ORGANIZATION A system incorporatingthe invention is describedin the following copendingapplications.

K. G. Spellnes, Communication Switching System, Ser. No. 230,887, filedOct. 16, 1962, now Patent No. 3,170,041; i

M. H. Esperseth et al., Communication Switching System, Ser. No. 240,497led Nov. 28, 1962, now Patent No. 3,275,752; n

K. E. Prescher et al., Communication Switching System Common Control,Ser. No. 231,625, led Oct. 19K, 1962, now Patent No. 3,173,994;

L. Bruglemans, Line Identifier Arrangement for a Communication SwitchingSystem, Ser. No. 231,425, filed Oct. 18, 1962, now Patent No. 3,211,837;

B. Sherstiuk, Sender for Communication Switching System, Ser. No.280,053,1iled May 13, 1963, now Patent No. 3,278,691.

Referring to FIG. 2, the system consists of the line group 100, groupselector 300, register-sender group 600, and the translator 700. Thereis also is a trunk group 500 which provides access from incoming trunkstothe registers, and acontrol center 790 which contains a specialcomputer for operation analysis and recording, and program upgradingequipment.

The signaling betweeny the system groups is accomplished by a techniquecalled di-phase. This method employs a phase shift technique for serialsending and receiving of pulses.

TRACING OF A LOCAL CALL As an introduction to the system operation, abrief description of a typical local call is processed through thesystem is now presented. The block diagram, FIG. 2, may be followed fortracing the call.

When a subscriber lifts the handset, the line group marker 200 goes intoaction `first by detecting the originating call mark, identifying thecalling line, and selecting an idle register junctor Within theregister-sender. A path is then temporarily established from the callingtelephone to the register junctor via the A, B, C, and R matrices, andthe subscriber receives dial tone. The dialed digits are storedtemporarily, coded, and processing is continued yas these digits arepassed to the translator 700, analyzed for type of incoming call, andinstructions are selected from the drum memory 730 and returned to theregister-sender 600 to guide further handling of the call. Upon receiptof the remaining digits, the translator 700 returns switchinginstructions corresponding to the called number as stored in the drummemory 730. The rinstructions are transmitted from the register-sender600 via one of the senders 671-680 and the originating junctor 120 k ofthey originating line group to the group selector 300.

In the group selector 300, the instructions are analyzed by the marker400, an idle terminating junctor 130 in the terminating line group islocated, and a path established to that line group via A, B, and Cmatrices of the group selector. The remaining instructions are followedby the line group marker to locate the called line terminals, select andseize a path from the terminating junctor through the E, D, B and Amatrices to the called line. The terminating junctor establishesringing, answer supervision, and talking battery for both parties whenthe call is answered.

Since the system is a common control operation, the markers of the lineygroup and group selector function only to serve the assigned portion ofthe call processing then for further service while only the talkingpaths are held through the switching matrices and junctors.

' THE LINE GROUP Line group switching network A trucking diagram of oneline group switching network is shown on the upper portion of FIG. 1.The network is made up of coordinate crosspoint matrices. This sectionof the system may be thought of as a large switching unit capable ofconnecting any one of 1000 lines originating calls to any one of 120circuits called originating junctors OI. Likewise, this unit is capableof connecting any one of 120 circuits called terminating junctors TI andrepresenting incoming calls to any one of the 1000 lines served by thisline group. Crosspoint matrices constitute the switching network andprovide concentration going outward for originating calls, and expansiongoing inward forterminating calls. For practical and economic reasons,three stages, A, B, and C, make up the outgoing switching stages. Fourstages, E, D, B and A, make up the incoming switching stages. The 1000subscriber lines divided into ten groups of 100 each, are located on themain distributingfframe and from there are jumpered directly to the Astage. No line intermediate distributing frame is required. The A stagehas 600 outlets or links (60 for each of the ten hundreds group)appearing as inlets to the B stage. The B stage, in turn, has 300 links(30 for each hundreds group) appearing as inlets to the C stage` The Cstage has 120 links to originating junctors. The originatingjunctorsprovide by-paths via the R stage to twenty-four registers and alsoprovide access to the inlet circuits 310 of the group selector 300. Withthis switching configuration, a fully equipped line group is capable ofhandling a maximumtraic of three unit calls per line in each directionat a grade of service better than .01.

The switching stage matrices are made up crosspoint reed relays, 15,000for a fully equipped 1000 line group or 15 per line (12 per line for twounit calls per line). As shown in FIGS. 3 and 4, the reed relay coil hastwo winding, an'operate (or pull) winding and a hold winding, and hasthree contacts. Two of the contacts switch the transmission loop. Athird locks the hold winding to the sleeve or C lead.

The subscribers line equipment is similar to a conventional line andcut-off circuit except that reed relays are used and fewer contacts arerequired. Reed relays were chosen over a static line circuit forsimplicity and reliability of operation and for electrical isolation ofelectronic apparatus from outside plant disturbances.

A maximum of thirty subscribers in a given hundreds group may be engagedin different conversations at one time.y One originating and oneterminating junctor, two each of A and B crosspoint reed relays, and oneeach of D, C, and E crosspoint reed relays Iare held in the line groupper conversation. Registers are held only during dialing.

The originating and terminating junctors mentioned earlier are reedrelay circuits performing several functions. The originating junctorprovides loop splitting facilities for an originating call. Initially, atransmission path is provided from the calling line to register and anadditional path is provided from register to group selector for earlyoutpulsing When the called line is reached, the originating junctorswitches the calling line through to the terminating junctor via thegroup selector. The circuit also provides a busy tone bridge in theevent of no link release to serve other calls. The register-sender 600and the translator 700 are functioning on a time division basis iavailability.

The terminating junctor performs functions necessary to extend the callto a called subscriber. yIt' provides a path into the line group markerfor signaling between the code receiver in the marker and the sendercircuit. The circuit provides regular or party line ringing controls,

ring back tone, and ring cut-off controls. When line busy isencountered, busy tone is provided at this point. It providestransmission battery feed for both called and calling parties. On testcalls and busy verification calls, the junctor removes the battery feedsand switches the calling line metallically through to the called line.For oicial calls, answer supervision is disabled within the junctor toprevent charging of the calling end. Thus, it is seen that specialservice calls are also handled by the terminating junctor via theregular switching network eliminating the need for a special switchtrain.

Line group marker Two markers 200 are always provided and the 1000 linegroups are divided between the two up to a maximum of ve line groups permarker. Each marker serves its associated line group matrices on anallotted basis, but, is also capable of assuming the load of itscompanion marker.

In its idle state, a marker continuously scans for requests for servicefrom the line groups with which it is associated. Upon recognizing -acall, either originating or terminating, in a particular line group, itlocks out all other groups via its allotter and allows the connectcircuitry of the selected group to switch in the matrix leads into themarker for processing. Approximately 400 leads are so controlled. AllIcalls in the allotted line group are4 processed before the markerreturns to its idle state to serve other groups.

When connected to a line group, the marker has two primary functions,connect a line originating a call through the matrices and originatingjunctor to a register and to connect a terminating junctor (representingan incoming call) through the matrices to the called line. Both reedrelays and electronic circuitry are used to perform these jobs. Theelectronic circuitry provides all logic and scanning operationsrequiring high speed. Reed relays are used merely for connectingpurposes, to switch in the necessary groups of leads into the electroniccircuitry for analysis. With this combination of components, theprocessing ofv a request for service by the line group marker isaccomplished in approximately 100 milliseconds.

For each function, the marker performs several tasks. In general, fororiginating traffic, it must provide line number identification,pathfinding and route selection, sending of line number identification,class of service, and line group identity. For terminating traffic, itmust provide terminating junctor identification, transceiver forcommunicating with the sender circuit, access to called line for busytest, PBX selection, and pathinding and route selection.

The tasks performed by the marker in processing a call are controlled bya sequence and supervisory circuit 290. This control may be compared toa programmed computer in that the marker follows a fixed plan ofoperation. All marker operations are governed by this control.

Included in unit 290 is the clock circuit which provides pulses tosynchronize operations within the marker and the timing circuitry whichis used to generate various time-out periods such as that providedbetween a reed relay operation and a succeeding electronic scanningoperation. Once the supervisory control recognizes a request forservice, either terminating or originating, it will process this callfrom beginning to end, locking out all other calls.

A two-Way communication path exists between the marker processing aterminating call and the sender circuit. In addition to receiving thecalled line number and any special instructions regarding the line, themarker may signal back to the sender any conditions peculiar to the linesuch as line busy, line idle, link congestion, recycle and send again,`and be referred back to the sender for appropriate action.

If on a terminating call, the marker transceiver received a PBX callindication, a PBX selector circuit marks all lines in the PBX group andenables the line identifier 6 to make a sequential test to select thefirst idle line. A maximum of 200 lines may be allocated within a 1000line group. for PBX service. Assignment of lines to a PBX group does notrequire consecutive numbering allocation.

THE GROUP SELECTOR Group selector matrix The intermediate switchingfunctions of the system are performed by a group selector 300, FIGS. 2and 7. Three stages of crosspoint switches are provided. The firstswitching stage 312, the A stage, contains 60 cards of 50 crosspoints,each arranged in a 5 x 10 matrix. This switching matrix is associatedwith the inlet circuit 310 line and cut-off reed relays to the groupselector. The second switching stage 314, the B stage, contains 60 cardsof 60 crosspoints each in a l0 x 6 matrix. The third stage 316, the Cstage, uses a basic arrangement of 60 crosspoints in a 6 x l0 matrix toprovide 600 outlets. The group selector has 300 inlets 310 serving theoriginating junctors in the line groups and incoming trunks.

The outlets of the group selector are arranged as 120 levels of l0trunks each. These levels may be combined to accommodate trunk groups ofany size.

Group selector marker The operation of the group selector is controlledby an electronic marker 400. The marker has control of all crosspointsin the group selector and sets up calls on a one-at-a-time basis. Themarker operates in response to selection digits received electronicallyin its transceiver 480 from the register-sender group. The holding timeof the marker is approximately milliseconds.

Operational description In its idle state, the group vselector marker iscontinuously scanning the group selector matrices for new calls. Theregister-sender group, via an originating junctor or incoming trunk,initiates a demand on a group selector by pulling the inlet line reedrelay. When associated with a matrix, the marker finding the inletdemanding service stops its scanning at that point and connects atransceiver to the demanding inlet. The routing digits are sent in highspeed code from the sender into -the marker transceiver. During thissame time, the marker operates connect reed relays to determine the linkavailability from the demanding inlet in the A stage toward the outletsthrough the B and C stages. Two routing digits are received by thetransceiver in the marker and extended to the trunk selection portion ofthe marker where connect reed relays gate idle test leads of theselected trunk group into the trunk scanning portion. Within thisscanner the link availability is combined with the trunk idle leads suchthat an idle trunk can appear idle to the scanner only if an appropriateidle link to the inlet exists.

If the trunk scanner finds an idle trunk, it pulls the proper groupselector crosspoints, checks to make sure that the selected truukbecomes busy indicating seizure through the group selector crosspoints,and clears its circuits.

THE TRUNK GROUP T rLmk group matrix The trunk group 500 (FIG. 2)provides access for incoming trunks from outside of the oice or forspecial intra-oice trunks such as operator or Wire chief. A trunk groupmatrix is capable of connecting any one of 75 incoming trunks to any oneof sixteen registers on a single output level basis.

Trunk group marker The operation of the trunk group matrix is controlledby an electronic marker 550 which has control of all reed relays andsets up connections ona one-at-a-time basis. The marker operates inresponse to a call for serv- THE REGISTER-SENDER The register-sendergroup 600 (FIGS. 2 and 7) is a time shared, common control unit with theability to register and process twenty-four simultaneous -calls. Thefully equipped unit consists of twenty-four registers and ten senders.

The registers operate in a time division mode. There is one registerjunctor for every register in the group. Real time to time `divisionentry is provided yby this circuit. A common control unit 664 comprisestime divided circuits which are shared by all twenty-four registers.These circuits are used yby each register in turn and are organized toprovide the needed registration and process control for the registers. Atemporary storage facility 660 is provided for the register group. Eachregister has an assigned storage area wherein all register informationis placed to allow time division operation by the common control. Afolded word oriented ferrite core memory is used for this purpose.`

The extension of the proper switching digits, to the line or trunkselection stages of the system and to other connecting exchanges, isaccomplished with a group of ten senders 671-4580; These senders operateunder the control of registers and are used to transmit information in adial pulse, multi-frequency, or code pulse manner.

Communication with the system translators, line group markers, trunkmarkers, and group selector markers is accomplished by high speed serialtransfer of digital information using diphase.

Circuit description In order to facilitate understanding the followingbrief description of each of the circuits within the registersendergroup is given.

The primary function of the register junctors 601-624 is to provide abuffer between the electronic equipment and the outside plantfacilities. As such, the circuit ernploys reed relays for all switchingfunctions, performing all those functions that require direct connectionto the calling line or trunk. These include dial pulse repeating, dialtone control, battery feed for the calling line or trunk, callingstation identification on party lines, test for coin deposit, coinrefund, and test for coin refund. The circuit also controls the switchtrain and provides for peg count and traic metering. Bothmulti-frequencyk and dial pulse junctors are used.

The sender circuits 671-680 provide means for transferring information(dialed digits or switching instruction) over the voice transmissionpath from the register- Sender to the office markers or to distantoffices. The sender is a universal sender inasmuch as it provides allmodes of sen-ding required by the system. Di-phase sending is employedfor transmission of switching instructions to the oflice markers. Thedi-phase part of the circuit is actually a transceiver 5400 since itprovides a means of receiving instructions from the markers as well as sendf ing to the markers.

For outgoing calls, the sender provides for both dial pulse andmulti-frequency signaling. The circuit operates in conjunction with thesender controller 670 which is common to all senders in theregister-sender group. The sender controller supplies the sender withthe digits to be sent out and indicates the mode of sending to beernployed.

The sender circuit is mainly an electronic circuit except or outgoingloop supervisory equipmentwhere reed relays are used.

The register receiver 630 is seized by the register controller `664 andassigned to serve the register junctor on a hold-til-nished basis. Thecircuit receives either the line number identification generated by theline markers or the trunk number identification generated by the trunkmarkers. On seizure of the circuit, a di-phaselink is established to themarker being served. When all the digits have arrived in the registerreceiver, the information is presented to the register controller forstorage in the area of the ferrite core array 660 associated with theregister being served. Upon completion of this storage process, theregister receiver 630 is released for use by the next register requiringservice.

The register controller 664, operating on a time division multiplexbasis, controls the progress of each call being processed. Within aparticular time slot, this circuit up-dates the information in storagein the section of the core array associated with the time slot register.

The register transceiver 690 operates as the communication device forinformation transfer between the register-sender group and the systemtranslators. It, like the register receiver, operates on ahold-until-nshed basis. This circuit provides two-way di-phase serialcommunication between the translators and the registersender group. Theorganization of this circuit is such that the transfer of informationfrom the read-shift buffer to the register controller is in a parallelmanner. Seizure is dependent on the condition of the control informationavailable in the carry buffer.

The sender controller 670 utilizing information available to it in theread-shift buffer, controls the ow of information to be sent by thesender in use. It forwards control signals to the proper senders such asmode of send signals, end of send signals, and release Signals. Itpresents to the senders the appropriate switching, and if necessary,dialed digits for proper routing of the subscribers call.

The sender assigner 683, on request of the register controller, willconnect an idle sender to the register junctor 'requiring service. Theconnection established by the assigner is the beginning of theterminating switch train, which will be extended by the system switchingstages on information received from the sender. The sender assigneroperates on a hold-til-nished basis.

THE TRANSLATOR LINE GROUPL AND MARKER-DETAILED DESCRIPTION the switchingmatrices and junctors in a line group.

The subscriber lines are connected on the horizontal inputs of the Amatrices, such that ten lines are connected at each A matrix. Thereforeten A matrices are provided for a group of lines. Also foreach hundredsgroup,

six B matrices are provided, each B matrix having one input connected toeach A matrix. Common to the ten hundreds groups or one thousand linesof a line group, there are thirty C matrices, and thirty corresponding Dmatrices. The connections are such that each C matrix and itscorresponding D matrix has its ten inputs connected to the ten differenthundreds groups. The verticals of the C matrices are c-onnected torespective originating junctors, with originating junctors 011-0130connected to the respective first verticals of the C matrices,originating junctors 0131-0160 connected to the second verticals of therespective C matrices, originating junctors 0161-0190 connected to thethird verticals of the respective C matrices, and originating junctors0191-01120 connected respectively to the fourth verticals of the Cmatrices.

The originating junctors each have one output connection to the IDF forconnection to the inlets of the group selectors, and another connectionto the R matrices. Originating junctors 1-20 are connected to therespective horizontals of matrix R1, originating junctors 0121-0140 areconnected to the horizontals of the matrix R2, continuing up to matrixR6 which has its horizontals connected to originating junctors01101-01120. There are four vertical links from each R matrix, or atotal of twentyfour, which are connected to the IDF for connection tothe register junctors in the register sender group 600. The registerjunctors in each register sender group are connected to the R matrixverticals of several different line groups.

The E matrices each have twenty horizontal links connected respectivelyto twenty diierent D matrices, with matrix E1 connected to lirstverticals of matrices D1-D20, matrix E3 having its first ten horizontalsconnected to first verticals of matrices D21-D30 and its second tenhorizontals connected to second verticals of matrices D1- D10. Matrix E3has its twenty horizontals connected to second verticals of matricesD11-D30. Matrices E4 to E8 are similarly connected to other links of theD matrices. The verticals of the E matrices, fifteen from each matrix,are connected to the terminating junctors.

All of the matrices are designated by reference -characters in which aninitial letter designates the switching stage. In the A and B stages theletter is followed by two numbers. The iirst number indicating thehundreds group and the second letter indicating the matrix within thehundreds groups. Thus in hundreds group one there are ten A matricesA11-A10 and six B matrices B11-B16. These A and B stages areinterconnected by links designated by the letters AB followed by threenumbers, in which the v first number indicates the hundreds group; thesecond number indicates the A matrix in the hundreds group and the thirdnumber indicates the B matrix in the hundreds group to which the link isconnected. Thus link AB111 of the first hundreds group connects card A11to card B11. The lines from the line circuits to the inputs of the Astage are designated by the letter I. followed by three digits, with therst number indicating the hundreds group, the second number indicatingthe A matrix within the hundreds group and the third number indicatingthe input of the A matrix. Thus lines L111-L110 are connected to the teninputs of matrix card A11. In the C stage the matrix cards aredesignated C1-C30, and in the D stage the corresponding D matrices aredesignated D1-D30. The links interconnecting the B stages to the C and Dstages are designated by the letters BC followed by three numbers. Thefirst number indicates the hundreds group of the B matrix and the lasttwo numbers indicate the C and D matrix, with a zero inserted as thecenter number for connections to cards yC1-C9 and D1-D9.

The links interconnecting the D and E stages are designated by theletters DE followed by three numbers. The first number indicating the Dmatrix with a zero preceding the matrix number for the matrices D1-D9,and the last number indicating the D matrix.

The schematic diagrams of FIGS. 3 and 4 show one or two crosspoint reedrelays of matrix cards of these stages;

and also a line circuit, an originating junctor and a tei*- minatingjunctor. Each link comprises four conductors, tip T, ring R, control C,and pull P. The tip and ring conductors provide an extension of thesubscribers loop for a talking path, the pull conductor is used tooperate the crosspoints, and the control conductor is used to hold thecrosspoints in a selected path. Between each horizontal link and eachvertical link of a matrix card there is a crosspoint switch comprisingthree make contacts in three capsules, two windings, and a diode. Toestablish an originating path after the marker has selected the route,an operate circuit is established on the pull conductor through thethree stages in series, through one crosspoint switch in each stage, tooperate the crosspoints, then a hold path is established on the Cconductor through the three crosspoints to hold the connections.

The line circuit LC111 comprises a line relay 12L having two windingsand a single make contact, and a cutoff relay 12C0 having a winding, twobreak contacts and a make contact. The tip and ring conductors of lineL111, which are connected to the subscribers loop, are also connectedvia the break contacts of the cutoff relay 12C0 through the windings ofthe line relay 12L to ground and negative battery respectively. Theconductor L111C is connected through the winding of the cutoff relay12C0 to negative battery. The conductor L111P is connected through themake contact of relay 12L and a resistor 1211 to conductor LRl to themarker; and also through the make contacts of the cutoiir relay 12C0 anda diode 1212 to conductor BCO to the marker. The conductors LRI and IBCOare multipled to all of the one thousand line circuits of the group.There is also a connection from the cutoff relay by an individualconductor WC111 to the marker, for wire chief use.

The originating junctor (FIG. 4) provides connections from theoriginating path from the C matrices by a line 011A through the junctorand line 011B and the R matrix to a register junctor, and line 011C tothe IDF for access to an inlet circuit of the group selector. Thetransmission path (conductors T and R) from the C matrix to the groupselector is split in the originating junctor. The incoming path isconnected to the register by leads TR and RR; and the outgoing path lbyconductors TS and RS to the sender. The contacts of relay 151B providethe split. Switching through of the connection from line 011A to line011C is accomplished -by operating relay 151B under control of theregister via lead ECR, which in turn causes the operation of relay 151A.

Holding of the preceding switch train by ground on the lead C of line011A is under control of the register junction via lead CR to relay 151Abefore cut through; and under control of the group selector via lead Cin line 011C to relay 151A after cut through. The R matrix is releasedafter cut through.

If a ylink busy condition is encountered, relay 15BT is operated by theregister junctor via lead BY to return link busy tone i.p.m.). Relay15BT remains operated under control of the calling group. No cut throughoccurs under this condition.

The terminating junctor (FIG. 4) provides access from a group selectoroutlet, via the IDF and line TJIA through the junctor to line T11B andthence through matrices E, D, B and A to a called line.

Battery feed is provided to the calling line by relay 18BF, and to thecalled line lby relay 1'7BF.

Busy-idle indication is provided on lead IT of line T11A for use by aparallel test circuit in the group selector marker.

Relay 17T1S when operated provides a path from the T0 and R0 conductorsof line T1 1A to conductors TC and RC of line T1C, which completes apath from the sender over the transmission path to the send receivecircuit in the marker. This relay is operated under the control of themarker by a signal on lead TJ. Relay 17T1S- also completes a path forthe ringing code signals l l from the send receive circuit on conductorsA, B, C and D of line TIC to the ringing control relays (not shown). Thejunctor is seized by ground forwarded via lead ECO of line TJ 1A tooperate relay 17S. This relay completes a path to ground to hold thepreceding switch train, and another path to ground to hold thesucceeding A B C D Gen. Ringing Connection Frequency l 0 1 T Fl l 0 l 0R F3 0 0 l 0 1 T F5 0 X 1 l T F1 Special Functions 1 1 0 1 Return linebusy (60 i.p.ru.).

0 X 1 1 No. ans. supy. (lQOFC operates).

1 X 1 1 No. ans. supy. or ringing (lQOFC) and metallic cutthru (19SPOoperates).

Ringback tone is supplied to the calling party during ringing. Busy tonefrom a 60 i.p.m. source is supplied to the calling party when the properbinary code as shown in the table is received from the marker to operatea busy relay (not shown).

In response to answer supervision a ring trip relay (not shown) operatesand shorts the winding of a relay (contacts only shown) which connectsthe called party to the voice transmission path. Relay 17BF thenoperates, and applies ground which extends through break contacts ofrelay 190FC (contacts only shown) to lead ECO of line T] 1A to repeatanswer supervision to the preceding switch train.

In response to one of the codes as shown in the table, relays 19SPC and190FC operate to provide a metallic path (T and R) free of attachmentsand inhibits ringing and answer supervision for verification, wirechief, and

routiner calls. In response 'to :another code, relay 190FC operates toinhibit answer supervision on calls to oflicial numbers, such as thetelephone company business oilice.

Release of the succeeding switch train may be controlled by a routiner.Opening lead EC releases the succeeding switch train but holds theterminating junctor seized. The terminating junctor is released whennegative battery potential is applied to lead EC.y

Release of the preceding switch train is delayed approximately 135'milliseconds after the calling party releases to protect againstunintentional interruption of the calling loop.

Timed disconnect of the preceding switch train and the terminatingjunctor 30 seconds after the called party disconnects is provided.

An arrangement is provided to permit the called party to hold thesucceeding switch train and the terminating junctor.

The line group connect circuit 148 is shown by triangles and trapezoidsrepresenting relay trees in FIGS. 3 and 4, and alsoin FIG. 1. The linegroup marker 200 is shown by a schematic and block diagram in FIGS. f

5 and 6, and also by blocks at the bottom of FIG. 1. For convenience inthe drawing, relays are shown having a large number of contacts althoughin the physical embodiment of this system the reed relay assemblies havebeen limited to ten contacts, and additional contacts are obtained byusing parallel and slave connected reed relays. A relay driver deviceshown symbolically in the drawings by a triangle with a line across itand associated ymake contact, -comprises a single transistorampliierwith a winding in its collector circuit and the single contactwhich is a reed` capsule operated by the winding.

The principal units of the line identier are a hundreds scanner 2903, atens scanner 2902, and a units scanner 2901. These units may be scannersor parallel ytest and lockout circuits which perform the followingfunctions: (l) a signal at any one of the inputs causes a devicecorresponding with this input to be set, (2) with one of these devicesin set condition signals at other inputs are inhibited from settingtheir corresponding device, and (3) the device in said position operatesa corresponding relay. Many circuits exist which meet theserequirements. 1n one chosen embodiment scanners operated under thecontrol of pulse sources and sequence state circuits in the sequence andsupervisory unit 290 have been used. The output devices comprise relaydrivers 2931-2940 from hundreds scanner 2903, relay drivers 2921-2930from tens scanner 2902, and relay drivers 2811-2820 from units scanner2901. The relays which are .operated under thecontrol of the relaydrivers are relays Hl-HO associated with the hundreds scanner 2903,relays rl`1-T0 associated with the tens scanner 2902, and relays U1-U0associatedwith the units scanner 2901.

Looking at the P leads of the horizontal inputs of a single one of thematrices such .as matrix C1, a negative potential applied to the P leadin any one of the line cir- .cuits can be detected through the diodesand pull windings of the A and B matrix cards, since the diodes areforward biased. Thus a negative potential applied to the P lead at anyline circuit of hundreds group 1 such as to conductor L111P, can bedetected at the first horizontal input of matrix C1, on conductorB=C101P. Likewise a call in any of the other hundreds lgroup of theG-line group will appear at a correspondingk one of the P leads of thehorizontal inputs of matrix C1. These leads are taken throughy contactsof relay HE, to the ten inputs of hundreds scanner 2903. Likewise inleach hundreds group the P leads of the horizontal inputs of any one ofthe matrices can detect a potential at any one of the ten lines lof theA matrix card connected -to that input. Thus in hundreds group 1 a callat any one of the lines L111 to L at the inputs of card A11 will appearat the conductor AB111P at the input of card B11. The ten leads AB111Pto AB101P from card B11 of hundreds group ABl (FIG. l) and thecorresponding ten leads from matrix card B11 of each of the otherhundreds groups `are taken through relay tree HEP which selects the tenleads of one hundreds group in accordance with the output of thehundreds scanner, and the ten leads are then taken through contacts ofrelay HE to the ten inputs of the tens scanner 2902. At the horizontalinput terminals of the A cards, allot` the lOOOP leads, ten from eachcard of the 100 A matrix cards, for example, leads L111P to L110P ofcard A11 of group ABl, pass through relay tree LS which selects the tenleads from one A matrix in accordance with the hundreds and tensselection, which are taken through contacts of relay LG and contacts ofrelay UP to the units scanner 2901. The inputs to each of the scannersaremultiplied to the other line groups as shown by the multiple symbols.

Sequence and supervisory circuits 290 The sequence and supervisorycircuits 290 include a sequence state register, miscellaneous ip-ops, anoperational timer, and a cycle counter, which supplysignals used by theother units in the marker. These circuits will be referred to in thesection describing the operation of the marker.

to transmit the hundreds,

' is parallel loaded via the send-receive circuit provides logic to Thesequence state iiow chart is shown in FIG. 12. On the flow chart eachyof the boxes includes the decoded designation of the sequence state atthe top and below it appears the binary code of ve flip-Hopsrepresenting that sequence state. The significance of each of thesequence states is explained in the section on operation of the linegroup marker. Briefly, states S2S13 are for originating calls, statesS14-S28 for terminating calls and states S29 and S30 are idle states. Atthe end of each call sequence state S29 is entered, and if there isanother call in the same line group state S1 is entered. If there is nocall in the same line group the sequence changes from S29 to S30, and ifthe allotter shows acall in another line group the sequence goes fromS30 to S29 to S1. If there is a terminating call it is given preferenceand state S14v is entered. If there is an originating call and noterminating call state S2 is entered.

Send-receive circuit 280 `shown in FIG. 8 as comprising an LNI shiftregister 4011,

an LNI encoder 4010l for parallel loading of the shift register, andlogic circuit 4012. The terminating call portion comprises a shiftregister shown by functional blocks extending across the bottom of FIGS.8 and 9, along with logic circuits in FIGS. 10 and 11. The commontransceiver 4100 is shown in FIG. 9, and comprises a receiver 4105,synchronizing circuits 4106, a transmitter 4107, and control circuits.

The LNI portion of the send-receive circuit is provided tens, units,class of service, and line group matrix identity of the originating lineinformation to the register sender group. This information LNI encoder4010 into the LNI shift register 4011. The relay driver 4101 closes itscontact e 4between resistance battery and the winding of relay 41LNI tothereby transmit a signal over lead BY, and as shown `in FIGS. 6, 4 and7,!through the relay tree RG to the register junctor y601. This signalis repeated via -circuits in the register junctor 601 and 4leadmultiplex 624 to the t register, which provides an acknowledgement byoperation of relay driver 5323 to put an additional ground via relay GOon lead BY, which causes relay 41LNI to operate. The information fromthe shift register 4011 is then transmitted serially using transmitter4107, through contacts 41LNI-1 and 41LNI-2 to conductors TR and RR andtransmitted through theregister junctor 601 into register receiver 630.

The terminating call shift register comprises ip-flop SUI, fourilip-iiops HU1-HU4 in FIG. 8, iiip-iiops TF1- TP4, iiip-op PRI, ip-flopBFI, and flip-flop BF2 in FIG. 9. Di-phase control -circuits and variouslogic circuits for terminating calls are shown in FIG. 10, and decodercircuits associated with the terminating call shift register are shownin FIG. l1. Logic is provided for loading and sending instructionsV (ie.trunk busy, resend, incomplete, etc.)

Ato the register sender group. Logic is also provided for checkingparity of the received data (even number of binary ones received), whichis accomplished by flipilops TM1 and PR2. These two flip-ops are usedfor both the originating shift register and the terminating shiftregister. Logic is also provided to clear and load data into the shiftregister.

' The code conversion for the terminating portion of the store theinformation received in the terminating shift register and to change thestored binary information into decimal form for use by the other linegroup marker circuits. This data constitutes the equipment locationidentity of a line or PBX group to t which the call will be terminatedand comprises the hunpriority hundreds group until it finds coincidencethe call is'in tens dreds decoder HT, tens decoder TT, units decoder UT,and the party digits and wire chief decoder. Special instructions suchas verification and wire chief are processed as part of the party digitinformation. Decoders PH, PT, and PU generate the PBX information. LogicAND gate 4207 generates the connect signal which is sent to the senderwhen the transmission path is established thereto. Logic AND gate 4210generates the incomplete or resend command which is decoded by thesender transmitter in the register sender group. Trunk busy, line busy,and line idle are generated by the sequence and supervisory circuit.Logic AND gate 4214 generates signal DZ which indicates all zeros in theshift register. Logic AND gates 4238 and 4229 generate command ZR whichis used by the sequence and supervisory circuit.

OPERATION OF LINE GROUP MARKER- ORIGINATING CALL The operationaldescription may be followed on FIGS. 3-7, or FIG. 1 may be used in placeof FIGS. 3-6 with FIG. 7, or FIG. 2 may be used.

Assume now that the subscriber at station S111 initiates a call. Inresponse to the closing of the subscriber loop, the line relay 12L ofline circuit LC111 operates and closes its contacts. Negative batterypotential through the break contacts of relay LR is applied overconductor LR1 yand resistor 1211 of line circuit LC111 and the contactsof relay 12L to the pull conductor L111P, thence through diodes and pullwindings on card A11, and card B11, to conductor BC101P at the input ofcard C1.

The potential is also applied through a diode and pull winding of cardC1 to the lead OJIAP of vertical V1, thence by way of conductor OC to aninput of the allotter 252. The allotter operates relay LG, and otherline groups are locked out.

The supervisory signal HF through contacts of relay LG operates relayHE. Relay HE prepares -operate circuits for the relay tree, connectsthrough the conductors BC101P to BC001P to the hundreds scanner 2903.

Referring now to the flow chart, FIG. l2, and assuming that the markerwas in the idle state S30, in response to signals LG and OC from theallotter, the sequence operation is started, going from S30 to S29 toS1.

- It is assumed that there is no terminating call, so the marker goes tothe originating call sequence, entering S2.

The marker determines whether there is a call in the 1. If the call isin other than hundreds group 1, a signal OCX is generated and steps thesequence to state S3, which causes a 10-step counter in the hundredsscanner 2903 to start and step of its output with a signal Iat onegofthe inputs to the scanner. The scanner then 0perates the correspondingone of the relay drivers 2931 to 2940, which places ground on lead HX-0.

However in our case the call is in hundreds 1, which is given priority,so a signal OCI is generated, and the sequence goes to state S4.

The signal S4 causes hundreds scanner 2903 to directly operate the relaydriver 2931 which supplies ground potential to operate the relay H1.Relay H1 locks to ground potential at break contacts of relay LKM.Ground potential through contacts of relay H1 completes the Operatingpath for relay tree HEP, connecting conductors AB111P to AB101P fromcard B11 via contacts of relay HE -to the inputs of the -tens scanner2902. A ground signal at contacts of relay H1 is transmitted by way ofconductor HX-0 and cable SS to the sequence Iand supervisory circuits290.

This causes the tens scanner to start counting. Since group l the tensscanner nds coincidence at step l and operates the relay driver 2921,which in turn supplies ground potenti-al to operate the relay T1. RelayT1 through its contacts locks to ground potential at break contacts ofrelay LKM.

1. IN A COMMUNCATION SWITCHING SYSTEM HAVING A PLURALITY OF LINES WITHLINE CIRCUIT INDIVIDUAL THERETO, HAVING A SWITCHING NETWORK FORSELECTIVELY ESTABLISHING ORIGINATING CONNECTIONS BETWEEN CALLING ONES OFSAID LINES AND ORIGINATING TERMINALS, AND TERMINATING CONNECTIONSBETWEEN TERMINATING TERMINALS AND CALLED ONES OF SAID LINES; AND HAVINGA MARKER COMPRISING LINE IDENTIFICATION APPARATUS WITH A PLURALITY OFIDENTIFICATION RECORDING DEVICES, AN ORIGINATING SELECTOR, A ROUTESELECTOR, A TERMINATING SELECTOR, AND A SIGNAL RECEIVER; MEANSRESPONSIVE TO A SERVICE REQUEST AT A CALLING ONE OF SAID LINES TO CAUSESAID MARKER TO ENTER AN ORIGINATING CALL CYCLE, MEANS ALSO RESPONSIVE TOSAID SERVICE REQUEST TO SET A PLURALITY OF SAID DEVICES OF THE LINEIDENTIFIER APPARATUS TO THEREBY RECORD THE IDENTITY OF THE CALLING LINE,MEANS TO CAUSE THE ORIGINATING TERMINAL SELECTOR TO SELECT AND RECORDTHE IDENTITY OF AN IDLE ORIGINATING TERMINAL, MEANS RESPONSIVE TO SAIDRECORDING OF THE CALLING LINE IDENTITY AND ORIGINATING TERMINAL IDENTITYTO CAUSE THE ROUTE SELECTOR TO SELECT AN IDLE ROUTE BETWEEN THEM, ANDMEANS TO CAUSE A CONNECTION TO BE ESTABLISHED THROUGH SAID SWITCHINGNETWORK VIA THE SELECTED ROUTE, THE MARKER THEN BEING RETURNED TO ANIDLE STATE; MEANS RESPONSIVE TO A SERVICE REQUEST AT ONE OF SAIDTERMINATING TERMINALS TO CAUSE THE MARKER TO ENTER A TERMINATING CALLCYCLE, MEANS ALSO RESPONSIVE TO SAID TERMINATING SERVICE REQUEST TOCAUSE THE TERMINATING SELECTOR TO SELECT AND RECORED THE IDENTITY OF THETERMINATING TERMINAL REQUESTING SERVICE, MEANS RESPONSIVE TO THERECORDING OF ITS IDENTITY TO CONNECT TO SIGNAL RECEIVER TO SAIDTERMINATING TERMINAL TO RECEIVE SIGNALS DESIGNATING THE DESTINATION OFTHE CALL, MEANS RESPONSIVE TO THE DESTINATION DESIGNATED BEING A PBXGROUP OF SAID LINES TO APPLY A MARK TO EACH IDLE LINE OF THAT GROUP,WITH EACH SUCH MARK APPEARING TO THE MARKER AS AN ORIGINATING CALLREQUEST, MEANS ALSO RESPONSIVE TO THE DESTINATION OF THE CALL BEING TO APBX GROUP TO PREVENT ACTUAL ORIGINATING CALL SERVICE REQUESTS FROM BEINGFORWARDED TO THE MARKER, MEANS TO ACTUATE THE LINE IDENTIFIER IN THESAME MANNER AS ON ORIGINATING CALLS TO SELECT ONE OF THE LINES HAVINGSAID MARK AND TO SET THE IDENTIFIER DEVICES CORRESPONDING THERETO, MEANSRESPONSIVE TO THE RECORDING TO THE IDENTITY OF A LINE BY THE LINEIDENTIFICATION APPARATUS AND THE RECORDING TO THE TERMINATING TERMINALBY THE TERMINATING TERMINAL SELECTOR TO CAUSE THE ROUTE SELECTOR TOSELECT AN IDLE ROUTE BETWEEN THEM, AND MEANS TO CAUSE THE SWITCHINGNETWORK TO ESTABLISH A CONNECTION VIA THE SELECTED ROUTE, THE MARKERTHEN BEING RETURNED TO AN IDLE STATE.